Recently our laboratory has demonstrated that the 3'-untranslated region (3'-UTR) of the cDNA of the bovine lymphokine interleukin- 2 (blL-2) acts as a lymphoid cell-specific gene regulatory element in vivo. Within the 3'-UTR we have identified a highly conserved nucleotide sequence motif, (TATT)n, that is also found in the 3'- UTRs of many other transiently expressed immunoregulatory genes of mammals. We have furthermore demonstrated that this conserved A/T- rich motif in blL-2 serves multiple functions in stimulated bovine lymphocytes, both at the DNA and RNA levels. At the chromosomal level the motif acts as the specific binding site for a nonhistone protein, HMG-1, and at the RNA level the conserved (UAUU)n cognate motif of the mRNA acts as a POSTTRANSCRIPTIONAL REGULATORY ELEMENT that determines the stability and selective degradation of blL-2 mRNA by serving as the recognition site for a specific nuclease(- s). Additionally, we have now isolated (from stimulated bovine lymphocytes) a large number of different UNKNOWN cDNA clones that contain the conserved motif in their 3'-UTRs and have many features suggesting that they may represent an as of yet unidentified group of lymphokine or growth factor-like genes. Furthermore, we have demonstrated that the cellular expression of the mRNAs of several of these unknown immunoregulatory genes are specifically modulated in lymphocytes infected with BOVINE LEUKEMIA VIRUS (BLV), AN HTLV- LIKE RETROVIRUS. The HYPOTHESIS TO BE TESTED by the proposed research is that these lymphokine gene regulatory mechanisms we have observed for the bovine system ARE ALSO GENERALLY APPLICABLE TO THE HUMAN LYMPHOKINE AND IMMUNOREGULATORY GENES CONTAINING THE CONSERVED A/T-MOTIFS AND THAT INFECTION OF HUMAN LYMPHOID CELLS BY HTLV AND HIV RETROVIRUSES MAY SPECIFICALLY MODULATE THE EXPRESSION OF THIS CLASS OF CELLULAR GENES. SPECIFIC AIMS of the research are to: (1) Investigate the possible in vivo posttranscriptional gene regulatory role of the 3'-UTRs of several REPRESENTATIVE lymphokine and immunoregulatory genes of human lymphocytes, including lL's-1, -2, INF-gamma, TNF and GM-CSF. (2) Characterize members of a group of CURRENT UNKNOWN immune-induced bovine cDNA clones containing the A/T-motif, particularly those clones who in vivo cellular genes are known to be specifically modulated by infection of lymphocytes by BLV. ISOLATE, CHARACTERIZE AND DETERMINE THE EXPRESSION OF A HOMOLOGOUS GROUP of cDNA clones from normal, HTLV-infected and HIV- infected HUMAN LYMPHOCYTES. (3) Directly investigate the role of THE TRANS-ACTIVATING tat PROTEINS OF HTLV-1 in the in vivo activation and modulation of the CONSTELLATION OF TRANSIENTLY EXPRESSED LYMPHOKINE AND IMMUNOREGULATORY GENES containing the 3'- UTR conserved A/T sequence motifs.